Horticulture Principles and Practices

3. Light. Many cacti are sun-loving plants. However, some prefer partial shade. As
previously discussed, some succulents are native to humid regions of the world. Light
intensity is critical because too much of it during winter can hasten the entry of some
species into their spring active growth phase. Photoperiod needs to cacti range
between twelve to eighteen hours. One practical way of “guessing” the light needs of
a cactus is by spine density. Those with fewer spines are more shade tolerant while
those with high spine density need high light intensity. Better still, one should consult
an expert or a reference source for the optimal light required for the species.
4. Fertilizing. Fertilizing is one of the least important inputs in growing and caring
for cacti and succulents. It is needed during the active growing season. Succulents
grow slowly indoors. Fertilizing them tends to promote undesirable elongation
and distortion in the shape of plants, reducing their aesthetic value. In lieu of
fertilizing, it is recommended for growers to refresh the growing medium by
periodically replacing old medium with fresh medium. Some commercially
formulated cacti fertilizer (e.g., 5-10-10, 7-10-6) are available. Fertilizers should
be low in nitrogen, and be applied sparingly about every two months.
5. Pests. Cacti rarely experience pest problems while growing in the open. However,
as indoor plants, some pests that may attack cacti include scales, mites, spider
mites, white flies, and mealy bugs. Cleaning the plant after the rest period to
remove dust particles, and also washing the roots under running water before
resetting in the pot, help to stave off some of these potential pest problems.
Insecticidal soaps or detergents should not be used.
6. Shrinkage. Shrinkage is part of the life cycle of many species of cacti. This
occurs over about four to six months involving both aboveground and belowground
structures. Plants that are still in their winter dormancy cannot make use
of water. Whereas shrinking accompanies winter rest, summer shrinkage may be
actually a call for water due to excessive due conditions.
7. Temperature. Desert cacti are adapted to warm conditions. However, extra indoor
heat during the winter period coupled with reduced light may cause cacti to grow
spindly and weak. A room temperature of between 7.22 and 18.3˚C (45 and 65˚F) is
desirable for cacti. The low indoor humidity during winter is especially intolerable
to jungle cacti, which need to be misted with water frequently during this season.
8. Cleaning. To keep plants attractive, cacti may be dusted, cleaned with a damp
cloth, or washed. These cleaning activities should be done very carefully when
handling species with thorns.
9. Repotting. Cacti require repotting every two to four years. To determine whether
repotting is due, the plant should be removed from its pot and its roots checked for
pot bounding.
14.10 M INIATURE ROCK GARDEN
Cacti are excellent plant species for creating rock gardens. They offer a wide variety of
plant shapes and forms and can be used to develop desert gardens. The garden is
created in a shallow container. The bottom of the container is lined with gravel or a suitable
drainage material and then covered with a potting mixture (Figure 14–29). Stones
of a variety of shapes and sizes are carefully chosen and placed to create a rocky terrain.
A variety of cacti (both desert and jungle) are selected and planted around the stones.
468 Chapter 14 Growing Succulents
14.11 GRAFTED CACTI
Cacti occur in a spectacular array of forms, as indicated in this chapter. The beauty
of these slow-growing plants can be enhanced by grafting different species with
contrasting forms and features onto one another (Figure 14–30). For example,